1. Field of the Invention
The present invention relates to an ophthalmic apparatus and, more particularly, to an ophthalmic apparatus which aligns an eye to be examined with an inspection unit using a joystick to inspect, observe, and capture the eye.
2. Description of the Related Art
Many ophthalmic apparatuses include a base unit having a face rest that fixes the face of an object, an inspection unit which observes/captures and measures the eye to be examined, a stage unit which moves the inspection unit in the backward/forward, leftward/rightward, and upward/downward directions relative to the base unit, and a joystick mechanism which is operated to drive the stage unit.
Many conventional ophthalmic apparatuses use a manual stage which mechanically links a joystick mechanism to a stage unit, and mechanically drive an inspection unit by using the joystick mechanism (to be referred to as the manual joystick hereinafter). Recently, there are an increasing number of ophthalmic apparatuses which include an electric stage driven by a motor or the like owing to advantages such as automatic alignment. Unlike a conventional joystick mechanism, the electric stage cannot be moved by using a mechanical link. For this reason, such an apparatus includes an electric joystick capable of performing control using electric signals as a drive instruction input device for an electric stage unit.
As a manual joystick mechanism, there is known a mechanism based on a scheme in which an examiner moves an inspection unit by tilting the operating rod on the contact point, as an operation supporting point, between a hemispherical support member disposed under the operating rod and a friction plate disposed on the apparatus base portion side. When wanting to largely move the inspection unit, the examiner increases the angle at which the operating rod tilts (to be referred to as a tilt angle hereinafter). When wanting to slightly move the inspection unit, the examiner decreases the tilt angle. The operating rod can tilt in all directions centered on a neutral point. It is possible to freely move the inspection unit based on the tilt angle and direction of the operating rod. In addition, the joystick used in the ophthalmic apparatus needs to have both the functions of performing fine motion operation required for alignment with the eye to be examined and coarse motion operation required for switching between the left and right eyes. When switching between the left and right eyes by using a joystick based on a scheme of manually driving the inspection unit, the examiner can easily switch between the left and right eyes by sliding the joystick on a friction plate. The examiner often performs this operation at the time of fine motion operation, and uses it to change the tilt angle of the joystick without moving the inspection unit. For example, this operation is used in the following case. After the left and right axes align with each other, the examiner raises the operating rod in a tilted state to the neutral state while sliding it with the inspection unit being fixed, and then performs alignment in the forward/backward direction.
On the other hand, there is known an electric joystick which electrically reads the tilt angle of the operating rod and drives the inspection unit based on the read information so as to obtain operational feeling similar to that obtained from the manual joystick scheme. A joystick based on this scheme is mechanically configured to make the inspection unit perform “fine motion” when being operated in a predetermined tilt angle range (for example, from −20° to +20°) and to make the inspection unit perform “coarse motion” when being operated beyond the predetermined tilt angle range (see Japanese Patent Laid-Open No. 2002-369799).
In addition, since the moving velocity of the inspection unit depends on the degree of skill in operation of the examiner, an electric joystick capable of changing the moving velocity of the inspection unit in the upward/downward direction is also known (see Japanese Patent Laid-Open No. 8-126611).
Joysticks are frequently used in the medical equipment field other than ophthalmic apparatuses. For example, a joystick is used to operate an endoscope. Joysticks capable of operating electric driving units are widely used in endoscopes to determine the bending directions of the distal ends of the camera units inserted into the human bodies. In the field of endoscopes, there have been disclosed many types of safety mechanisms for preventing the endoscope distal end portions inserted into the human bodies from damaging the bodies due to operation errors. As an example of a safety mechanism, there has been disclosed an intention detection unit which allows the examiner to input information which is provided, in addition to a joystick, for an endoscope (see Japanese Patent Laid-Open No. 2003-230535). According to Japanese Patent Laid-Open No. 2003-230535, a combination of an input from the intention detection unit and an input from the joystick is used to determine whether joystick operation is intended by the examiner or an operation error. The endoscope validates or invalidates the input instruction by joystick operation based on the determination result, and then controls the bending operation of the endoscope distal end portion.
The joystick disclosed in Japanese Patent Laid-Open No. 2002-369799 which operates the electric stage unit and the apparatus disclosed in Japanese Patent Laid-Open No. 8-126611 allows operation more similar to the operation of a conventional joystick mechanism based on the manual driving scheme.
The electric joystick disclosed in Japanese Patent Laid-Open No. 2002-369799, however, gives no consideration to the sliding operation of this manual joystick. For this reason, if the left and right axes align with each other when the operating rod has a given tilt angle, it is necessary to perform tilting operation back and forth while maintaining the tilt angle. This poses a problem that an alignment shift tends to occur in the leftward/rightward direction at the time of alignment in the forward/backward direction, resulting in difficulty in operation. When an integrated joystick is configured to implement coarse motion and fine motion, it is necessary to tilt the operating rod through a predetermined angle or more at the time of coarse motion. For this reason, when coarse motion has switched to fine motion, the operating rod has always tilted. It is difficult to raise the operating rod to the neutral state without moving the inspection unit from the position at which it has stopped at the time of coarse motion.
In addition, moving velocity settings are limited to those in the upward/downward direction in the apparatus disclosed in Japanese Patent Laid-Open No. 8-126611, and no consideration is given to the easiness of alignment in forward/backward and leftward/rightward motions.
The operation error prevention mechanism presented in the apparatus disclosed in Japanese Patent Laid-Open No. 2003-230535 is effective in an apparatus in which the movable range of an operation target coincides with the operation range of the joystick. For this reason, it is difficult to apply such a mechanism to an apparatus like an ophthalmic apparatus which requires fine motion operation and coarse motion operation and in which the moving range of the inspection unit is sufficiently larger than the moving range of the joystick. In addition, no consideration is given to a sliding mechanism.
In consideration of the above problems, the present invention provides a technique of implementing an electric joystick with a simple arrangement which has operability similar to the sliding operation of a manual joystick.